The purpose of our proposal is to make our collection of aligned amino acid and nucleotide sequences of proteins of immunological interest available to the research community and to continue our analyses of these sequences for structure and function relation-ships. The 1991 Fifth Edition of "Sequences of Proteins of Immunological Interest" consists of 2597 pages in three volumes. During the past year and a half, our data have increased by more than 50%, making a printed version of a Sixth Edition prohibitive. Therefore we have initiated a collaboration with NCBI, NLM, NIH which has allowed the electronic version of the Fifth Edition to be freely available to the research community. Two data forms, Postscript and ASCII text are currently being assessed as possible means for distributing the database. PostScript format allows researchers to print desired up-to-date pages of the book in the Fifth Edition format. The ASCII text version will be converted to ASN.1 by NCBI. Both files can be updated weekly. This new approach of data distribution will need careful investigation. Our study of CDR sequences in relation to antibody specificities has indicated that CDRH3 amino acid sequences seem to be uniquely associated with specificities while the other five CDR sequences are less restricted. We have started to categorize CDRH3s according to their lengths and functions in order to analyze the problem of antibody complementarity. Similar studies will be extended to the other CDRs. Our previous finding of identical FRs between human and mouse may become valuable tools for humanizing rodent antibodies. We have subgrouped Tcr alpha and beta chains, and further divided these subgroups into families, trying to understand the structure and function of these molecules. There is a possibility that Tcr chains may fold somewhat differently from antibody molecules. Aligned MHC class I and II sequences and process peptides will be studied by our variability analysis. Hopefully, our results can be correlated with experimentally determined three dimensional structures.